In the scorching Jerusalem summer heat, armed Israeli police raid an apartment searching for a child missing since 2008. Ten-year-old Michael Bitton is thought to have been abducted in one of Israel's highest-profile international custody battles. Among those helping the police in their hunt is former joint-head of the Manchester Community Security Trust, Joel Tobias.

With CST he directed security operations for the city's Jewish community. Now as a computer forensic investigator, Tobias runs the multi-million pound company CY4OR. He flew to Israel in July last year to bring his modern form of criminal investigation to bear on the search. Rather than looking for fingerprints or DNA, the Manchester-based investigator searched for cyber-clues - remnants of data stored on computers and mobile phones which could lead to information on the whereabouts of the child. This time, however, his investigation was unsuccessful.

Back on British soil, Tobias's firm has just cracked a major high-tech fraud case for cable-TV giant Virgin Media. Last month three Birmingham men were jailed for up to five years after computer forensic investigators proved they were illegally modifying television set-top boxes to receive cable channels for free.

By far CY4OR's most serious job to date was the case of Dr Mohammed Asha, the suspected mastermind behind the 2007 car bombing of Glasgow airport. Tobias's team proved Asha's innocence from hidden information in Microsoft Word documents, known as "meta-data".

"We proved he hadn't accessed some of the illegal content that had been put onto the computer by somebody else," Tobias says.

The 42-year-old Mancunian goes on to explain that his company deals with 40 counter-terrorism cases a year, working with MI5 and police forces around the country. All 14 of his investigators have police security clearance. Tobias is naturally cagey about revealing details of what kind of high-tech surveillance services his men offer.

"We've got five ex-military staff. Let's just say there are capabilities out there that would make you say: 'Hmm, that's interesting'," he says, turning to his computer screen and finding the location of his personal iPhone on a satellite map in seconds.

"That's not secret agent stuff, that's an Apple service we can all buy for £50 a year. So you can imagine what can be done," he adds.

In the Glasgow bombing, police found the bombers and prosecuted one of them by matching data lifted from their mobile phones against a database jointly used by MI5, MI6 and GCHQ, the government's eavesdropping centre. "The technique can be used on most of our mobile phones," explains CY4OR's laboratory director, Chris Vaughan.

"You get the last GPS fix recorded by the mobile. An iPhone will tell you where you used an app last. We can then find the locations and plot a map of what this iPhone has been used for and where."

Tobias can recover memory of websites visited, information downloaded, photos taken and conversations made, even if the mobile phone's memory has been completely erased.

Terrorism, however, is not the largest criminal activity Tobias and his team are asked to tackle. Of 700 criminal cases investigated annually, up to 80 per cent involve child pornography, he says. "We do masses of child abuse, which is proving horrific to work on. People think child pornography is revealing photos of little 15-years-olds in short skirts. It's much worse."

CY4OR's temperature-controlled store room at the company's offices is filled with computers recovered from police raids. The team's job is to find pictures and videos the computer users have attempted to delete.

Most of the images are recoverable using special software which can also spy on what internet connections have been made. It can reveal the network of distribution over the internet to lead police to the source of the images.

But the only known way to tell if pornography involves children is by the human eye. Investigators spend much of their time confined to private computer booths with caution signs to warn other staff members that graphic material is being viewed.

Exposure to these images can take its toll. "We have a retained councillor and all staff who are working on child abuse cases have to go and see him," says Tobias.